Studies on axonal (axoplasmic) transport are proposed to further the understanding of the development and maintenance of synaptic connections. Axonal transport is a basic element of neuronal protein metabolism, since it supplies macromolecules synthesized in the cell body to regions of the neuron unable to synthesize them. Axonal transport of protein is especially important during axonal elongation and synaptic development when protein demand is high and the variety of proteins needed may be changing. Transneuronal transfer of "trophic" materials may also be important at this time. Experimental approaches in this proposal are centered on analysis of the rates, polypeptide composition and turnover of axonally transported proteins in the developing mammalian visual system. Special emphasis will be placed on analysis of axonally transported nerve ending proteins before and after the onset of functional visual activity. Proteins which will receive particular attention are tubulin (the dimeric protein of neurotubules) and the (Na ion plus K ion)-dependent ATPase, which is the basis of the active transmembrane transport of Na ion and K ion. If time permits, transneuronally transferred material will be investigated in neonates and adults.